Vena cava filters are metallic devices that catch blood clots to prevent them from traveling to the lungs and causing a pulmonary embolism.
These devices usually are used when drug therapy, such as treatment with blood-thinners, has failed or is considered inadequate or when drug therapy would cause other dangerous medical conditions.
Implanted vena cava filters safely and effectively reduce the risk of pulmonary embolism in most people.
Usually, the consistency of blood remains liquid enough for the blood cells and other molecules to travel smoothly through the arteries and veins. Sometimes, however, clots will form in a process called coagulation. When clots or other blood-borne clumps of tissue migrate through the circulatory system, they are called emboli; a single migrating clot is called an embolism.
A pulmonary embolism is a clot that travels through the venous system and eventually lodges in the pulmonary artery, which carries blood from the heart to the lungs. This can obstruct the blood supply to the lungs, which is potentially fatal and should be treated as an emergency.
Many pulmonary emboli result from a condition called deep vein thrombosis (DVT). DVT is the formation of a blood clot in the veins embedded deep in the muscles, usually in the lower leg and sometimes in the pelvis or groin.
Vena cava filters, tiny nets, help prevent emboli from traveling through the heart and into the lungs. Most commonly, vena cava filters are inserted into the inferior vena cava, a large vein that carries blood from the lower extremities.
WHEN IS THE PROCEDURE INDICATED?
People most likely to receive a vena cava filter are those at risk for pulmonary embolism and those for whom drug or other therapy is considered inadequate. Vena cava filters are also inserted to protect trauma patients from pulmonary embolism associated with their injuries.
To diagnose DVT and pulmonary embolism, physicians perform a physican exam and may order imaging tests, such as:
Ventilation perfusion scan (VQ scan);
Computed tomography (CT) scan; and
Magnetic resonance imaging (MRI).
Patients who are receiving filters are likely to receive anticoagulants prior to the procedure to reduce the risk of clot formation.
WHO IS ELIGIBLE?
Patients eligible for vena cava filters include those who have chronic risk factors for developing pulmonary embolism, such as DVT, and those who are about to have surgery.
Trauma patients whose injuries put them at risk for pulmonary embolism but who may have lost too much blood to be given blood thinners are also eligible for vena cava filters.
WHAT TO EXPECT
The physician administers a local anesthetic at the insertion site, either the arm, neck, or groin, and makes an incision. Patients may also receive a muscle relaxant for additional comfort. Alternatively, the procedure may be performed while the patient is under general anesthesia.
The physician inserts the collapsed filter into the incision via a catheter (a long, thin, flexible tube) and advances the filter to the vena cava. The physician then deploys the filter in the vein at the target location, removes the insertion device, and closes the incision. The procedure generally takes from 10 to 40 minutes. Antibiotics are prescribed as necessary to minimize the risk of infection.
POST-PROCEDURE GUIDELINES AND CARE
Patients are likely to remain in the hospital until the supervising physician confirms that the filter is properly fixed in the vena cava and that there are no complications from the procedure.
The presence of a vena cava filter does not affect daily routines or the use of other medications. Some patients may remain on anticoagulant drug therapy to reduce the risk of post-insertion clot formation, or risk enlarging a pre-existing clot.
Vena cava filters are 98 percent successful in preventing symptomatic pulmonary embolism. However, they can be associated with surgical and anesthesia complications, although these are infrequent.
These complications include:
Bleeding at the insertion site;
Anesthesia-associated complications such as an allergic reaction or breathing problems;